1. Field of the Invention
The present invention involves an inflatable passive restraint system for restraining the occupants of a moving compartment, such as an automobile, in the event of a collision or other sudden and severe deceleration. Such systems, generally referred to as airbag systems, have become increasingly popular in modern motor vehicles.
This invention provides an improved airbag system which contains fewer component parts, including fewer fasteners, and generally requires fewer manipulations, is easier and less expensive to assemble than similar prior art airbag systems.
2. Description of Related Art
Airbag systems usually comprise a module containing four major components, an inflatable airbag cushion, an inflator to provide the inflation gas for the cushion, a cover deployed over the cushion and adapted to open when the inflator is activated, and a connecting structure such as a reaction canister, housing or mounting plate to hold and orient the components. Such systems are provided in different configurations dependent upon where they are to be mounted and the space available in the particular model vehicle for which they are intended. Airbag systems intended to protect an automobile driver are typically mounted on the steering column directly in front of the driver, while those intended to protect front seat passengers are usually mounted behind the instrument panel, or dashboard.
Prior art airbag modules have typically been assembled by attaching each of the cushion, the inflator and the cover to the housing, canister or mounting plate by a plurality of bolts, rivets or other fasteners. A number of such fasteners are required to distribute the inflation forces about the cushion mounting so that the cushion does not leak and is not torn due to a concentration of inflation forces at too few mounting locations. The multiple joining operations, each requiring orientation of the components to be joined and the application of multiple fasteners, results in a relatively complex and expensive assembly procedure. Moreover, these operations are a major cause of manufacturing defects which require that the assemblies be either reworked or discarded.
A number of systems have been developed to facilitate the assembly process. For instance, U.S. Pat. No. 5,388,858 discloses a module which additionally includes a retainer member to hold the components in position once it is attached by deforming a portion of the housing. U.S. Pat. No. 5,634,658 discloses a simplified method of assembling the module which mounts the airbag cushion by compressing it between the module housing and the inflator. U.S. Pat. No. 5,520,409 discloses a method of attaching the cover to the housing by using a band of heat shrinkable material, while U.S. Pat. Nos. 2,755,125; 3,853,334 and 4,111,457 describe the use of a clamp and, in the last patent, an elastic strip, to attach the cushion to the housing. U.S. Pat. No. 2,850,291 describes the use of a ring to attache the cushion to a ring nut which is attached to a casing containing liquid carbon dioxide. U.S. Pat. No. 5,560,643 discloses attaching the cushion around the inflator by providing a stiffening collar ring in the cushion adjacent to its opening and then clamping the cushion about the periphery of the inflator by deforming a clamping structure partially about the portion of the cushion containing the stiffening collar ring.
Notwithstanding these developments, the need to provide reliable airbag assemblies containing fewer components and requiring fewer operations during the assembly process continues.